Method of coating metal



L. SIMCNS METHOD OF COATING METAL Filed- Oct. 3. 1940 June 1, 1943.

patented dune i, 1943 stares earner ora menus or codeine rim-frat.

Leon Simona, New York, N. Y. Application @ctoher a, rare, Serial No. eraser a manna. (ct. eta-re) face layer may be discontinuous and of varying thickness.

The invention relates particularly to copperclad wire, rod, and the like, although it is not copper anterior the extrusion zone or at the inlet end of the extrusion zone, and congealing said molten copper against the outer surface or the core. A superior non-corrosive bond is thus secured between the steel core and the initial layer of copper which has been thus congealed. The initial copper layer which has been thus provided bonds readily with'the main portion of limited to any pafilcular materials or combinations of materials. V

The core preferably consists of low-carbon steel which is paramagnetic so that said core can he heated by the hysteresis efiect'. However, said core may be made of any metal or of any alloy whose melting point is above the extrusion temperature or the surface layer. If the core is made of steel, said core may be treated, after the surface layer has been formed, so as to transform the steel core to the austenite stage. This type of steel is generally known in the trade as austenitic steel." Austenlte is a solid solution of FeC in gamma iron. austenite can be obtained by quenching 1.50% carbon steel by means of water which has a suitable low temperature. Austenite also occurs in steel which contains 10% of manganese, and it also occurs in steel which contains 25% of nickel, after suitable slow cooling. The carbon content of the austenitic steel may he as high at 2%. The outer covering or surface layer of said core is preferably resistant to corrosion and it may consist of copper or a copper alloy or am corrosion-resistant suitable metal or alloy which has a high-melting-point. "the surface layer may he made or a metal or alloy which is not resistant to corrosion. Likewise the coating of the core may he formed in two or more layers. These coating layers may he formed of identical metals or alloys, or of different metals or alloys. Another object of the invention is to pro dune copper-clad steel bodies or the like, at very low cost, by a direct extruding operation,

non-molten metal for producing the suriface layer, thus eliminating the expense of melting large bodies or metal and congealing the molten metal around the core so as to provide a non=ccrrosive hand. according to my invention an eriicient non-corrosive bond is secured between the core and the surface layer, without melting the metal or alloy which is used to make the surface layer. However, and as later explained herein, a thin surface layer of copper may he termed on the core by melting suficlent the surface layer which is secured by extrusion.

Another object of the invention is to provide the main surface layer of thecoatlng by an extrusion process which can be utilized within substantially wide limits of temperature, so that the crystal size of the coating metal or alloy can be readily controlled.

Another object of the invention is to control the crystal sizeand formation oi the core itself, by forming the main surface layer within a suitable temperature range. 4

The coating i' aterial is preferably a metal or alloy whose melting point is at least 657 8., this being the melting point of Metals or alloys whose respective melting points are substantially 657 C. or above, are designated as high-melting-point metals or alloys.

Other objects of my invention will he set forth in the following description and draw ng which illustrate a preferred embodiment thereof, it being understood "that the above statement of the objects of my invention is intended gen erally to explain the same and without limiting it in any manner. a

The drawing, diagrammatically illustrates an apparatus which can be used for practicing the invention.

Heretoiore in making copper-clad steel wire or steel rod, the invariable large-scale commercial practice has been to pour molten copper into a mold, around a steel billet of relatively large diameter. The molten copper was thus eongealed around the core, in order to form a jacket. it was then necessary to roll or otherwise work this composite billet down to size. Ti-his rolling operation is expensive because it is necessary to anneal the composite billet after one or two worlrings, as otherwise it becomes too hard for further working.

According to my invention, rod of relatively small dameter can be directly coated with the copper or the like by means of an extrusion process, so that the amount of working which is necessary to reduce the coated core to final size is greatly reduced, in addition to other advan= tages.

it has been well-known "for many years to threads. The plug 4 is provided with a tapered outlet bore 3, which serves as an extrusion nozzle. The cylinder I is made of any suitable material which is preferably not-paramagnetic, so that magnetic flux can-readily pass through said wall to the interior, of said cylinder. The cylinder I may be made of the so-called non-magnetic steel whose formula is 74% iron, 18% chromium, 8% nickel.

A piston 5 is movably located in the cylinder I. This piston I is also preferably made of material which is non-paramagnetic.

A first hollow coil 6 is located around the outer wall of the cylinder I. This coil 8 is connected to a suitable source of high-frequency alternating current of the type which is used in induction furnaces. The coil is cooled in the conventional manner by forcing water or oil or other cooling medium through the same. This oil-may be a non-conducting mineral oil. The drawing shows the inlet pipe I of the coil 6, and the outlet pipe 8 of said coil, through which water or oil or other cooling medium is forced. This coil 6 heats the entire extrusion zone and it may also be located partially anterior the extrusion zone, so as to heat the core C anterior the inlet or right-hand end of the extrusion zone.

As an example, the core C may be made of low-carbon steel, and said core may be steel rod whose diameter is 0.500 inch. The core C is preferably, but not necessarily, 'made of paramagnetic material. This core C is preferably sufllclently bendable or flexible so that it can be unwound from a suitable reel, and the finished material can also be'wound on a suitable reel if desired.

A practical working example will be given in connection with the coating of the core C with a layer Ca of copper. The copper mass 9 is loaded into the cylinder I in the form of granules or powder or the like. It may consist of masses of any size, and it may also consist of an integral slug which flts snugly in the cylinder I and which is bored so as to make it possible to pass the core C through the same. The copper mass 9 is subjected to suitable extrusion pressure by means of the piston 5, which is actuated by hydraulic pressure or in any other suitable manner.

The melting point of pure copper is 1083 C. or approximately 1981" F.

Copper can be softened by heat, without melting the same, in order to enable the copper to be readily extruded under suitable pressure, at a temperature as low as 1300 F., thus affording a temperature range of more than 600 between the extrusion point and the melting point of the copper. The preferred temperature of the copper, during the extrusion thereof, is at or above 1600" F.

The-supply of heat through the induction coil 6 is regulated so as to maintain the copper mass 9 at the extrusion temperature under the applied pressure. The pressure which is applied by the piston may be as high as 50,000 pounds per square inch. Under said pressure and at said extrusion temperature, the copper is extruded in the form of a surface layer or jacket Ca.

The head 5a of the piston 5 serves as a stop because it is of greater outer diameter than the bore at the rear wall of the cylinder I. Therefore, the extrusion is stopped before the mass of copper is used up.

In order to provide a superior non-corrosive bond between the extruded copper sleeve Ca and the core C,,said core C may be given a very thin initial coating of copper or of other material, directly at the surface of said core, which is compatible with copper so that the extruded copper will form a non-corrosive bond with the initial very thin layer of copper. The core C can be given a thin initial coating of copper either by electrolysis, or in any other suitable manner.

The core C may be additionally heated by a' source of heat which is independent of the induction coil 6. For this purpose I have provided shoes I0 and II which contact respectively with the core C. The core C can slide readily relative to these shoes III and II. The shoes I0 and II are held yieldingly against the core C by respective springs Ito and I8.

The single shoe I0 may be replaced by any suitable number of shoes which are arranged circumferentially around the core C in order to equalize their pressure and the same may be done with the shoe II. The shoes I0 and II are connected by means oi. respective wires I2 and It to any suitable source or current which may be direct current or alternating current of any frequency.

The shoes I0 and II are preferably made of graphite or any other suitable material of highmelting-point.

The shoes I0 and II are preferably located in lateral bores of the piston 5, and said shoes are insulated from the piston 5. Said shoes are located slidably in respective metal bushings I5 and lid; which are respectively located in bushings I8 and lid, which'are made of a suitable refractory insulating material. Each of the metal bushings I5 and lid is thus electrically insulated from the piston I. The outer ends of the respective metal bushings I5 and I511 are closed by means of respective removable plugs I1 and Ila, and said shoes are respectively provided with springs I8 and lid which force the respective shoe inwardly against the adjacent portion of the surface of the core C.

Of course the coil is suitably insulated from the cylinder I, either by spacing the coil 6 from the cylinder I, or in any suitable manner. It is preferred to insulate the coil 6 from the cylinder I, merely by spacing the same from each other.

The high-frequency current of the coil 6 rapidly heats that part of the core C which is located in the extrusion zone, and it also heats a part of the core C which is anterior the extrusion zone. This heating is due partially to eddy currents, and it is due partially to the rapidly alternating hysteresis efl'ect which is produced by the highfrequency alternating magnetic flux which Is Passed through the respective part of the core C. The indirect heating which is thus secured is sufflcient to maintain'that part of the core C which is advanced through the extrusion zone, at the desired temperature. The temperature of the core in the extrusion zone may be from 1300 F.

to 1900 F. The temperature of the core in the extrusion zone is preferably not less than 1800 E, and save for the exception later stated hereat the desired extrusion temperature.

in. the temperature of the core in the extrusion is preferably below the melting point of the copper. Therefore. the iacket Co is formed .ouhti by the con or ricn-moltm cop- However. the temperature of the core in the outreach zone may he equal to the melting mint oi the copper and eyen a little above the meltins' pcmt or the copper, as long as the lat heat oi the core in the extrusion zone is cient to melt the main mass or the copper in the eutrusion zone. As the core is thus advanced continuous@ through the extnision zone, a t m" er or molten copmr may he formed directly at the surface of the core,hut the main mass of the jaclret is formed by extrusion oi the nonmolten copper.

The frequency or the current which is supplied to the coil t through its cooled leads, is of the usual frequency which is used in high-frequency induction furnaces. The wattage oi the current which is supplied to the coil 6 necessarily depends upon the size or the apparatus and other yariahle factors, such as the cross-sectional di= meter or the core, the cross-sectional diameter oi thecopper mass and iron, etc.

eddy current which is-induced by the coil also heats the cylinder l, the copper mass 9, and the piston t. The copperis thus heated by the coil t to the extrusion temperature, but not above the melting point.

The core 6 is pulled or pushed continuously through the extrusion zone, at a regulated rate,.

so that said core is maintained at the extrusion temperature within the extrusion zone.

' However, the core may have a temperature gradient within the extrusion zone, so that the core has a higher temperature at the inlet end at the extrusion zone than at the outlet or lefthand end of the extrusion zone. For this purpose the core and its jacket may be suitably cooled extely to the plug l.

Tile part of the core C which contacts with the copper at the inlet end of the extrusion zone may he maintained at a temperature which is equal to the melting point oi the copper br shove the melting point of the copper, and the part or the core which is located adjacent and at the outlet end of the extrusion zone may have a temperature which is less than the melting point or the copper but which is within the limits of the extrusion temperature. The core C and is ,taolret Ga are preferably maintained at a temperature of about 1600 152, as said core and jacket pass out or the nozzle 3 of the plug i. The core and its jacket are then cooled externally to outlet end oi the extrusion zone, so as to produce the austenite in the steel core C.

The supplementary coil to is of the same type as the coil (i, and said coils 6 and do may be supplied with current from the same source. The pipes la and to correspond respectively to the pipes l and The coil to may supplement the action of the heating current which is supplied to the shoes ill and i l, or it may replace said shoes iii and it, which can be omitted from the apparatus. The coil to heats the core (3 anterior the extrusion zone. The heat which is supplied hy the coil can therefore he sumcient merely to maintain the copper in the extrusion zone The coil Grl'heats the adjacent part oithe core 6 to a temperature which may he equal to or above the extrusion zone, and which raises the temperatom 0! the respective part of the core above the melting point'ot the copper. is merely sumcient to melt enoughcopper to-form a very thin initial layer which congeals very close to the inlet or t end oi the extrusion zone.

IITM l kv-r' the extrusion, the core 0 is preferably insul ted tr the around, by mounting the mage reel and the take-up reel on. insulated supports. The dra shows a copper mass a ct greater cross-sectional diameter than the crosssectional diameter of the core C, but this relation may he reversed, or said diameters may he equal 1 r u plying a heating current through the wires it and it. or in any other manner, or due to the hysteresis efiect alone, the temperature of the core C in the extrusion zone may be above the temperature of the copper in said extrusion zone. temperature of the core in the extrusion zone may he less than or equal to or even above the melting point of the copper, thus melting the copper directly at the surface of the core in the extrusion zone to form a very thin initial layer which conceals against the core anterior the nozzle 3, while substantially all the copper in the extrusion zone is non=molten.

If the-copper is thus melted directly adjacent the core or against a part of the core in the ex-' trusion zone, the outflow or the copper in molten to through. the tip of the extrusion nozzle is prevented, because the copper jacket or layer conseals to solid jacket i'orm before passing out of the nozzle and preferably before-entering the nozzle it. p

The latent heat of the molten copper at and adjacent the er or right-hand end or the nozzle t is readily and rapidly dissipated through the plug t and the wall of the cylinder 1!. Coolins means, such as a jet of water or oil or gas can he used to cool the jacketed core, external to the nozzle it, or the plug l may be directly cooled, in order to prevent molten metal from 1 passing out of the nozzle. The temperature or Bil the copper mass may be higher at the inlet end oi the extrusion zone than at the outlet end thereof, it the extrusion zone is of suihcient ax ial length, and the copper at the outlet end of said zone is thus cooled. The core can fit snugly in the bore of cylinder 5.

The surface of the core need not be coated with copper by electrolysis or the like, prior to passing the core through the extrusion zone, as this is optional. a a

The surface which is to be coated in the extrusion zone must be very clean, and free from oil or the like. i

till

the melting point of the copper. The additional A thin coating oi copper which has been melted and then congealed is thus formed against the core, anterior the outlet end of the extrusion zone, and the major part of the coating is formed by extrusion in the rest of the extrusion zone.

The jacketed core may be cooled external to the plug t, by a spray of water or other cooling a ent.

The use of an induction coil is preferred because it enables convenient and accurate regulation of the heat, and because the hysteresis efiect makes it possible to maintain a paramagnetic core at a higher temperature than nonpararnaanetic coating material. The core 6 may he of any desired length and thicmess, and it may he a relatively short and rigid rod, oi the kind which is used in lightning arresters and the like.

It is thus possible in some cases to produce an article of finished size by means of the extrusion apparatus. However, it is preferred to mechanically work the coated core, to an extent sufliclent to produce the desired crystal formation in the copper. This mechanical work is done in the cold, by rolling or drawing, since coldworking produces the desired crystal formation.

The fit of the core in the bore of the piston should be sufficiently tight to prevent any reverse flow of the solid or molten copper. The inlet or right-hand end of the bore of the piston may be tapered so as to act like a die, and slightly reduce the core C at said inlet end, producing the desired close but sliding fit of the core in the bore of the piston.

The drawing is wholly diagrammatic and it is not intended to be to scale. The axial length of the extrusion zone which is filled by the copper mass 9 may greatly exceed the transverse diameter of said space. The portion of the core which thus contacts with the couper in the extrusion zone or space, can thus be made sufllciently long to provide the desired temperature gradient, whereby either the core or the copper, or the core and the copper, are at a higher temperature at the inlet or right-hand end of the extrusion zone than at the outlet or left-hand end of said extrusion zone, For this purpose the extrusion isstopped before the mass of copper in the extrusion zone has been forced completely out of said zone, and while maintaining said temperature gradient. The longitudinal axis of the apparatus may be vertical and the extrusion nozzle may be at the bottom of said apparatus, in order to facilitate the removal of the piston from the cylinder, in order to insert a new charge of copper to be extruded.

While the invention relates particularly to forming a surface layer or coating from metals which have high-melting points, the invention is broad enough, in certain of its aspects, to cover the use of metals oralloys of relatively low-melting points.

It is one of the advantages of the process-that the steel which passes out of the extrusion zone is at a suitable temperature, about 1600 F., so that the steel can be cooled to produce the austenitic stage.

If the core has a diameter of 0.500 inch, the core and its jacket can be subjected to the usual cold working to an extent sufllcient to diminish the diameter of the core to .460 inch without annealing the core. crystals of the copper the desired size and formation. By forming the jacket by extrusion on a core of sufiiciently small diameter, the core can be reduced to convenient commercial size without the necessity of stopping the cold working in order to anneal the steel core, thus greatly diminishing the cost of production 01' the finished article.

This cold working gives the While it is preferred to advance the core co: tinuously through the extrusion zone, said movi merit of the core through the extrusion zone me be intermittent.

More than of the jacket Co is formed is extruding non-molten metal, and as much I 99% of the weight of the mass of the jacket Cl and even more, can be formed by extruding nor molten metal.

The invention is by no means limited to a extrusion process because it is novel to heat th core to a temperature which is above the meltin point oi! the metal of the jacket, and to regulat the amount 01' heat which is supplied to the cor so as to form a thin initial bond of congeale molten metal, while the major part of the jacke remains in the non-molten condition during th connection of the jacket to the core.

Whenever I refer in the claims to coating 1 metal core with covering metal, said coverim metal may be applied directly to the bare suri'ao of the core, or the core may have any desire intermediate non-metallic covering material.

The supply of alternating current to the coil 1 is regulated by any suitable conventional mean: so as to maintain the metal mass 9 in the nonmolten but extrudible condition.

y I have shown a preferred embodiment or my invention, but it is clear that numerous change: and omissions can be made without departim from its spirit.

I claim:

1. A method of covering a metal core with a sleeve of covering metal, which consists in advancing the core through an extrusion zone and while contacting the core with said covering metal in the extrusion zone, extruding the covering metal out of said extrusion zone in the form of a jacket around said core, heating the core in said extrusion zone by means 01' an electric current, indirectly heating the covering metal in said extrusion zone by means of said electric current to extrusion temperature while maintaining the covering metal which is located in said extrusion zone and which is spaced from the core at a tem pertatlure below the melting point of said covering me a 2. A method of providing a paramagnetic core with a covering jacket of covering metal which is substantially non-paramagnetic, which consists in advancing the core through an extrusion zone in contact with the covering metal, heating the covering metal in said extrusion zone by means of eddy currents, also heating the core in said extrusion zone by means of eddy currents and hysteresis so that more heat is supplied to the core than to the covering metal in the extrusion zone, and forcing the major part of the covering metal in non-molten iorm out of said extrusion zone in the form of a jacket around said core.

LEON SIMON S. 

